This forum needs your help: you got hints from the community and now you have fixed your code? dont just reply with "now its fixed" or "i found the error"! please take the time to post also an detailed answer with the working code.

The setCollapsible(boolean) doens't seem to effect the center panel, only the other 4 panels (east, west, north, south).

the expand() and collapse() API of the ContentPanel doen't seem to work either (at least they don't collapse/expand properly), I have to use expand(LayoutRegion) and collapse(LayoutRegion) on the BorderLayout.